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Results for “Maximal Midexpiratory Flow Rate”

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PubMed1989

Dose-response relationships of intravenously administered terbutaline in children with asthma.

The bronchodilator effect of three successive stable plasma terbutaline levels was studied in 10 children with asthma. Each terbutaline plateau was achieved by giving a rapid intravenous infusion of terbutaline, 0.9 microgram/kg, followed by a continuous infusion for 2 hours. Mean plasma terbutaline concentrations (18, 36, and 53 nmol/L at the three plateaus) were found to correlate linearly with the maintenance dose of terbutaline (2.4, 4.5, and 6.3 micrograms/kg/hr, respectively). Mean forced expiratory volume in 1 second increased from 65% to 96%, and mean forced mid-expiratory flow from 32% to 71% of the predicted normal value during the study (p less than 0.01); maximum bronchodilation was obtained at mean terbutaline levels of about 30 nmol/L (range 20 to 60). Effective plasma terbutaline levels were associated with side effects such as headache and tremor in all patients. In addition, heart rate increased from 84 to 116 beats/min, systolic blood pressure rose from 115 to 129 mm Hg, and diastolic blood pressure dropped from 72 to 61 mm Hg during the study. We conclude that a loading dose of 2 micrograms terbutaline per kilogram of body weight over 5 minutes, followed by a continuous infusion of 4.5 micrograms terbutaline per kilogram per hour, is suitable for treatment of severe bronchoconstriction in children. Because of interindividual variations in drug metabolism and clinical effect, dose adjustment should be evaluated at regular intervals.

Adolescent↗

PubMed1998

Beta2-adrenoceptor regulation and bronchodilator sensitivity after regular treatment with formoterol in subjects with stable asthma.

OBJECTIVE: We have previously found that beta2-adrenoceptor downregulation and bronchodilator desensitization to albuterol occurred at 36 hours after stopping regular treatment with twice daily salmeterol. In this study we have evaluated these same effects with formoterol given once or twice daily on a regular basis. METHODS: In a randomized, placebo-controlled, double-blind, double-dummy crossover study, 16 subjects with mild-to-moderate stable asthma (mean [SD] age, 32.5 [15.3] years; mean [SD] FEV1, 73.2 [12.1] percent predicted) receiving regular inhaled corticosteroid therapy received 1 week of treatment with formoterol dry powder (24 microg twice daily [8 AM/8 PM]), formoterol (24 microg once daily [8 PM]), or identical placebo. Lymphocyte beta2-adrenoceptor parameters and a dose-response curve to inhaled albuterol (200 to 1600 microg) were evaluated at 36 hours after the last dose of each treatment period. RESULTS: There were no significant differences in the mean values for albuterol dose-response effects among the three treatment regimens. Comparison of maximal bronchodilator responses between treatments (mean and SEM as change from baseline) revealed no significant differences between treatments for FEV1 (0.47 L [0.06 L] for placebo vs 0.48 L [0.07 L] for 24 microg once daily formoterol vs 0.51 L [0.08 L] for 24 microg twice daily formoterol) or for forced expiratory flow, mid-expiratory phase (FEF25-75) (0.80 L/sec [0.12 L/sec] for placebo vs 0.80 L/sec [0.16 L/sec] for 24 microg once daily formoterol vs 0.89 L/sec [0.14 L/sec] for 24 microg twice daily formoterol). Formoterol also had no significant effect on mean lymphocyte beta2-adrenoceptor density. However, in five of seven patients with the homozygous Gly-16 polymorphism, beta2-adrenoceptor density was downregulated by twice daily formoterol, whereas only two such cases exhibited a reduction in maximal FEV1 response to albuterol. CONCLUSIONS: The results of this study showed that for patients taking inhaled corticosteroids, overall beta2-adrenoceptor regulation and associated bronchodilator sensitivity to inhaled albuterol were unaltered at 36 hours after stopping regular treatment with formoterol. However, in a subset of patients who were Gly-16 homozygous, there was a tendency towards downregulation but not desensitization. Further studies in subjects with more severe asthma are required to assess the clinical relevance of these findings.

Administration, Inhalation↗

PubMed1998

Effect of dental treatment on the lung function of children with asthma.

In this preliminary study, the authors evaluated whether dental treatment can trigger a reaction in the hyperactive airways of children with asthma, thereby affecting lung function. They also examined the variables, if any, that predict a change in lung function in relation to dental treatment. They tested the lung function of 57 6- to 18-year-old subjects with histories of active asthma, using spirometry before, immediately after and 30 minutes after routine dental treatment. Results revealed a statistically significant decrease (P < .05) in lung function and a clinically significant decrease in lung function in approximately 15 percent of the subjects.

Adolescent↗

PubMed1999

Pulmonary and auditory function among experienced construction divers: a cross-sectional study.

We studied pulmonary and auditory function in a cross-sectional study of 26 experienced construction divers compared with 26 workshop workers matched for age, height, and smoking habits. The divers used air as breathing gas and performed open-sea bounce dives to a maximum of 50 m in sea water. The mean number of dives over a mean diving period of 20 yr (SD = 11) was 4746 (SD = 4743) (Range: 450-17000). Assessment of lung function included dynamic lung volume and flow and diffusion capacity (transfer factor) for carbon monoxide (TlCO). The auditory examination was performed measuring air conduction thresholds in a cabin. The results show a significantly higher mean forced vital capacity (FVC) of 6.01 L (SD = 0.88) in the divers compared with 5.67 L (SD = 0.84) (p = 0.045) in the controls, and an alveolar volume (VA) of 7.74 L (SD = 0.99) in the divers compared with 7.35 L (SD = 0.74) (p = 0.035) in the controls. There was a nonsignificant reduction in forced mid-expiratory flow rate (FEF25-75%) and a significant reduction in forced expiratory flow rate at 50% of FVC (FEF50%) among the divers of 4.69 L (SD = 1.41) compared with 5.76 L (SD = 2.03) among the controls of (p = 0.03). There were no differences in FEV1 and TlCO between the two groups. The divers showed reduced auditory function in their left ear compared with their right ear in the 3 kHz (p = 0.006) and 8 kHz (p = 0.022) area. No statistical difference was found in hearing thresholds of the divers compared with those of the controls. Our results indicate that exposure to diving may be associated with changes in pulmonary function and that the left ear may be more vulnerable than the right ear to hearing impairment in construction divers.

Adult↗

PubMed1985

[MEF test--an instrument for the determination of maximal expiratory flow values PEF, MEF 75, MEF 50, MEF 25].

For reduction the working extent in measurement and classification of flow-volume curves a device was developed which calculates and indicates digitally the maximal expiratory flow values PEF, MEF 75, MEF 50 and MEF 25 directly from the flow in forced expiration. We have used an approaching calculation method whereby the expense of realization was low. By a comparative examination of 172 patients, it could be found that the device has a sufficient measuring accuracy and is advantageously applicable to clinics and screening.

Computers↗

PubMed1996

Pulmonary function in Sardinian fire fighters.

Our study examined the respiratory function of 92 firemen whose main activity is fire fighting in forests and open country. Such fire fighting activities are to be considered a risk to the respiratory tract, taking into account studies already in the literature that have evaluated the nature and quantity of inhalable toxins present in activities of this kind. The control group was composed of 51 Carabinieri (policemen), who were asked to fill in a questionnaire about their work activities. Forced expiratory volume and flow, total lung capacity, respiratory volume, and the permeability of the alveolar-capillary barrier were measured. Firemen and Carabinieri (policemen) showed FVC rates higher than the European Community for Coal and Steel standards. The firemen showed a significant reduction in forced expiratory volume in 1 second (FEV1)[3.90 (0.50) vs. 4.04 (0.44); p < 0.05] and forced expiratory flow at 75% of forced vital capacity (FVC) (FEF75) [8.37 (4.11) vs. 8.38 (1.67) p < 0.05] and more markedly in the FEV 1/FVC relationship [80.07 (5.89) vs. 83.89 (1.67) p < 0.001] and in FEF50 [4.73 (1.34) vs. 5.54 (1.44) p < 0.01] and FEF25[1.58 (.47) vs. 1.99 (.69) p < 0.001]. There were no marked differences in air-blood exchanges. No correlation was found between respiratory function data and years of service or the number of fires extinguished during work experience.

Adult↗

PubMed1998

Respiratory findings in synthetic textile workers.

We studied 308 female and 92 male textile workers employed in a factory that produced synthetic fiber hosiery. The mean age of the women was 38 years, their mean duration of employment 16 years. The mean age of the men was 39 years with a mean duration of employment of 16 years. A control group of 160 female and 78 male nonexposed workers was also studied. Chronic and acute work related symptoms were recorded for all workers. Ventilatory capacity was measured by recording maximum expiratory flow-volume (MEFV) curves from which the forced vital capacity (FVC), the 1-sec forced expiratory volume (FEV1) and maximum expiratory flow rates at 50% and the last 25% (FEF50, FEF75) were read. There was a higher prevalence of all chronic respiratory symptoms in exposed than in control workers, although the differences were statistically significant only for dyspnea, sinusitis, and nasal catarrh (P < 0.01) in female synthetic textile workers, and for nasal catarrh (P < 0.01) in male synthetic textile workers. Occupational asthma was recorded in 3 (0.9%) of the women textile workers, and in 1 (1.1%) of male textile workers. There was a high prevalence of acute symptoms during the work shift, which was greatest for cough (female: 46%; male: 59%), dryness of the throat (female: 49%; male: 40%), dryness of the nose (female: 53%; male: 43%) and eye irritation (female: 46%; male: 36%). Ventilatory capacity data among the synthetic textile workers demonstrated significantly decreased FEF75 compared to predicted (P < 0.05). Our data suggest that inhalation of dust in synthetic textile plants causes the respiratory impairment.

Adult↗

PubMed2001

Comparison of normal infants and infants with cystic fibrosis using forced expiratory flows breathing air and heliox.

SUMMARY. The detection of early airway disease in infants with cystic fibrosis (CF) may lead to earlier intervention and an improved prognosis. We hypothesized that the ratio of maximal expiratory flows while breathing a mixture of helium and oxygen (heliox) and air, referred to as density dependence (DD), would identify early airway disease in infants with CF who have normal lung function. We also hypothesized that these infants with CF might be better differentiated from normal infants when the flows breathing heliox are compared instead of room air flows. We evaluated 10 infants with CF and 21 infants without CF and with normal lung function, defined as a forced vital capacity (FVC) and forced expiratory flows between 25-75% of expired volume (FEF(25-75)) of greater than 70% predicted (z-score > -2.0). Full forced expiratory maneuvers by the rapid thoracic compression technique were obtained while breathing room air and then heliox. Flow at 50% and 75% of expired volume (FEF(50), FEF(75)), FEF(25-75), and FVC were calculated from the flow volume curve with patients and control subjects breathing each gas mixture. The ratio of heliox to air flow at FEF(50) and FEF(75) was calculated (DD(50), DD(75)), and the point where the two flow-volume curves crossed (V(iso) V') was also measured. DD parameters did not distinguish the infants with CF from the infants without CF; length-adjusted FEF(50) breathing air was significantly lower in the infants with CF compared to the infants without CF (P < 0.05). Length-adjusted flows breathing heliox did not distinguish the two groups. We conclude that the lower FEF(50) value may reflect early airway obstruction in healthy infants with CF, and that measurements obtained with the less dense gas mixture did not improve detection of airway disease in this age group.

Air↗

PubMed1987

Airway response to salbutamol and to ipratropium bromide after non-selective and cardioselective beta-blocker.

Eight healthy men were randomly assigned in a latin square order to receive single doses of placebo, tertatolol 5 mg, propranolol 80 mg and atenolol 100 mg at 7-day intervals. Resting heart rate and pulmonary function were measured 10 min before and over the 240 min following dosing, and then 15 min after inhalation of salbutamol 200 micrograms and ipratropium bromide 40 micrograms. The three beta-blockers caused similar reductions in resting heart rate throughout the study, whereas placebo had no effect. The three beta-blockers, like placebo, produced no significant change in pulmonary function during the 240 min after dosing. The bronchodilator response to salbutamol after atenolol and placebo was preserved, whereas it was reduced after administration of either of the non-selective beta-blockers, tertatolol and propranolol. An unequivocal response of the airways to ipratropium bromide was observed after tertatolol and propranolol, which was much greater than after atenolol. No response was observed after placebo. Thus, despite bronchial beta 2-blockade, by non-selective beta-blockers, bronchodilatation was definitely produced by ipratropium bromide, confirming the predominant role of the parasympathetic system in the autonomic innervation of normal human airways.

Adrenergic beta-Antagonists↗

PubMed1985

Measurement of reversibility of airways obstruction: which parameters to use?

Maximum expiratory flow-volume (MEFV) curves recorded before and after salbutamol inhalation on 100 patients with various lung diseases were studied. Improvement was found to occur more frequently in MEF50, FEF25-75, FVC and MEF25, than in FEV1, FEV1/FVC%, or MTT. If improvement in only one of the first four parameters was taken as a measure of reversibility of airways obstruction, many cases showing improvement in the others were missed. Improvement in any of the last three parameters was rarely missed if improvement in any of the first four was present. It was concluded that there is no single best measurement for assessment of bronchodilator response. FVC, FEF25-75, MEF50 and MEF25 should all be measured. A flow-volume record of forced expiration from which all these measurements can be derived would therefore be preferable for this purpose to the time-volume spirometer record from which only FVC and FEF25-75 can be determined.

Adolescent↗

PubMed1979

Changes in pulmonary function after naturally acquired respiratory infection in normal persons.

Changes in pulmonary function due to naturally occurring respiratory tract infection were examinated in 26 normal healthy volunteers during a period of 6 months. Forced expiratory maneuvers in each volunteer were recorded at 2-wk intervals throughout the study and daily during illness. Significant impairment of peak expiratory flow rate, forced vital capacity, forced expiratory volume in one second, and maximal mid-expiratory flow rate at 50% of the vital capacity was observed during infection, whereas changes in the maximal expiratory flow rate at 75% of vital capacity were nonsignificant. From these results, we conclude that large airways are certainly affected during uncomplicated respiratory infections in normal healthy persons and from the changes observed in FVC we suggest that more widespread involvement of the small airways may occur.

Adolescent↗

PubMed1980

Density dependence of maximal expiratory flow in chronic obstructive pulmonary disease.

Pulmonary mechanics were studied in 22 patients with chronic obstructive pulmonary disease (COPD) who had no evidence of asthma. Eleven of the 22 patients had a density dependence of maximal expiratory flow within the reported normal range. Patients with normal density dependence (responders) were not different from those with decreased density dependence (nonresponders) in mean age, smoking history, symptoms of cough or dyspnea, maximal expiratory flow at 75, 50, and 25% of the vital capacity during air breathing, total lung capacity, or static elastic lung recoil at 50% of the vital capacity. The nonresponders had smaller vital capacity values, larger ratios of residual volume to total lung capacity, higher resistance, and lower static recoil at total lung capacity. There was a correlation between diffusing capacity for CO and density dependence. There was an inverse relationship between the change in density dependence after inhalation of isoproterenol and initial density dependence. Dysanaptic lung growth and increased compliance of the central airways are potential mechanisms for normal density dependence in these patients. The prevalence of normal density dependence in these patients with established COPD raises serious questions concerning the usefulness of density dependence in the early detection of COPD. The differences in density dependence may indicate differences in pathogenesis of the airflow obstruction and hence may be of prognostic significance.

Airway Resistance↗

PubMed1980

Usefulness of forced expiration slope ratios for detecting mild airway abnormalities.

To assess their value for early recognition of airway abnormalities, forced expiration slope ratios as recently defined by Mead, were measured at 5 lung volumes in 114 healthy nonsmokers and in 76 cigarette smokers. In healthy nonsmokers, slope ratios were independent of sex and body height, but were significantly correlated with age. They tended to be higher at low lung volume, particularly in older subjects. In male smokers with a tobacco consumption of less than 5 pack-years, slope ratios were increased at both ends of the volume range, suggesting nonhomogeneous lung emptying and peripheral airway obstruction. With increasing tobacco consumption, slope ratios tended to return to normal values at low lung volume, perhaps because of airway closure. In female smokers, slope ratios were decreased at high lung volume and increased at low lung volume, suggesting that both central and peripheral airways were abnormal. Mead's analysis appeared to be a useful tool for discussing the data in terms of functional abnormalities. However, because of their large variability, slope ratios were not as successful as transit time indices for recognizing abnormal subjects.

Adult↗

PubMed1997

Short-term variations in oscillatory and spirometric lung function indices among school children.

The aim of this study was to compare immediate, daily and weekly variation in respiratory resistance measured by means of the forced oscillation technique (Rrs,FOT) to spirometric indices in 7-12 year old children with chronic respiratory symptoms. The lung function measurements were performed in 19 children on 4 days, i.e. two consecutive days during two consecutive weeks. On each day, the measurements were carried out at the same time of day and always repeated three times. In addition, Rrs,FOT and spirometric lung function indices were compared with an exercise challenge test in 12 children. Intrasubject coefficients of variation (CoVs) for Rrs,FOT were larger than those for spirometric indices. Only in the immediately repeated measurements was the CoV of maximal expiratory flow at 25% vital capacity larger than that of Rrs,FOT (16.6 vs 14.9%). At all time intervals, the smallest CoVs were observed in forced vital capacity (FVC) or in the ratio of forced expiratory volume in one second to FVC (2.0-2.6%). When excluding Rrs,FOT values which were not within 2 SD (0.11 kPa.L-1.s) of the differences between the immediately repeated measurements, the CoV of the immediately repeated measurements of Rrs,FOT was reduced to 9.1%, being smaller than that of maximal mid-expiratory flow (10.1%). However, even then the day-to-day variation in Rrs,FOT was clearly larger (16.0%) than those of the airflow indices at specified lung volumes (7.2-8.3%). This was also true for the weekly variation. In the exercise challenge test, there were larger changes in Rrs,FOT values than in the spirometric indices, but Rrs,FOT was the most sensitive index to detect changes in the respiratory system. In conclusion, the variation in Rrs,FOT values was larger than that of most spirometric indices. When a reliability index was applied, the immediate variation in Rrs,FOT values was comparable to those of the airflow indices at specified lung volumes. Rrs,FOT was also the most sensitive index in the exercise challenge test, and therefore it seems to be suitable for detection of short-term functional changes in the respiratory system. However, the relatively low repeatability of Rrs,FOT over days and weeks may limit its applicability to longer-term follow-ups.

Airway Resistance↗

PubMed1993

Pulmonary function and hypoxic ventilatory response in subjects susceptible to high-altitude pulmonary edema.

To determine if spirometric changes reflect early high-altitude pulmonary edema (HAPE) formation, we measured the FVC, FEV1, and FEF25-75 serially during the short-term period following simulated altitude exposure (4,400 m) in eight male subjects, four with a history of HAPE and four control subjects who had never experienced HAPE. Three of the four HAPE-susceptible subjects developed acute mountain sickness (AMS), based on their positive Environmental Symptom Questionnaire (AMS-C) scores. Clinical signs and symptoms of mild pulmonary edema developed in two of the three subjects with AMS after 4 h of exposure, which prompted their removal from the chamber. Their spirometry showed small decreases in FVC and greater decreases in FEV1 and FEF25-75 after arrival at high altitude in the presence of rales or wheezing on clinical examination and normal chest radiographs. One of the two subjects had desaturation (59 percent) and tachycardia during mild exercise, and excessive fatigue and inability to complete the exercise protocol developed in the other at 4 h. The six other subjects had minimal changes in spirometry and did not develop signs of lung edema. Further, we measured each subject's ventilatory response to hypoxia (HVR) prior to decompression to determine whether the HVR would predict the development of altitude illness in susceptible subjects. In contrast to anticipated results, high ventilatory responses to acute hypoxia, supported by increased ventilation during exposure to high altitude, occurred in the two subjects in whom symptoms of HAPE developed. The results confirm that HAPE can occur in susceptible individuals despite the presence of a normal or high ventilatory response to hypoxia.

Adult↗

PubMed1991

[Standards in evaluating the test of obstruction reversibility based on the flow-volume curves].

The study analyzed the changes in the shape of the flow-volume curve after fenoterol (Berotec) inhalation in school age healthy children. Significant increase of FEF25-75%, FEF50%, FEF25% values were seen. The authors demonstrated that bronchodilatation was not related to sex, height, weight and children's age, but it's value is indirectly proportional to the at-rest state of the airways. It seems, basing on results of this study, that FEV1 and FEF25-75% are the best indexes of dilatation tests. Increases of 10% and 30% are significant of bronchodilatation.

Adolescent↗

PubMed1979

Pulmonary function and maximum exercise responses following acute ozone exposure.

We examined changes in pulmonary function during resting exposure to concentrations of ozone at 0.75, 0.50, 0.25, and 0.00 parts/million (ppm), and determined the effect these exposures had on a subsequent maximum exercise test using filtered air. In order to determine if recovery of pulmonary function would be facilitated by increased ventilation due to maximum exercise, a control condition was conducted with subjects resting for a period equivalent to the maximum exercise condition. Eight males and five females participated in eight different conditions in order to answer these two questions. Resting 2-h exposure to 0.75 and 0.50 ppm ozone caused significant decrements in forced vital capacity of 10% and 5%, respectively. However, 0.00 and 0.25 ppm ozone induced no pulmonary decrement. None of the pollutant conditions reduced subsequent maximum exercise performance (ml O2.min-1.kg-1, heart rate, and total performance time). The pulmonary function responses after the maximum capacity test returned to pre-ozone values for the 0.50 ppm condition, but were still significantly decreased for the 0.75 ppm condition. The increased ventilatory exchanges from maximum exercise did not facilitate the return of pulmonary function. It appeared that increased ventilation during ozone exposure plays a significant role only in inducing pulmonary function decrement, but not in facilitating the return of pulmonary function to normal values.

Adult↗

PubMed1975

[Maximal mid-exiratory flow (MMEF) in the evolution of the respiratory functional patter of silicosis. (author's transl)].

A follow up study of VC, FEV and MMEF was performed by the authors in forty silicotic patients, mainly in order to find out if MMEF were more sensitive than VC and FEV 1 IN detecting respiratory function impairment in the follow up of silicosis. In patients with moderate bronchial obstruction, a statistically significant difference was found between themean values of MMEF measured in two different instances: such a finding suggests a greater MMEF reduction in the early stages of silicosis. In 22 subjects with moderate respiratory function impairment (VC and FEV1 less than or equal 40% predicted values), MMEF was found to be, percentually, more decreased than FEV1: the difference was statistically significant. It is therefore concluded that MMEF changes in the follow up examination of silicosis are more sensitive than other functional indexes.

Forced Expiratory Flow Rates↗